Printable Magnetic Receptive Composite Sheet and Method of Making

ABSTRACT

Printable magnetic receptive composite sheets are made by calendering a thin layer of a magnetic composition and bonding it to a top printable layer on one or both sides of the magnetic layer wherein the calendered layer has a thickness up to 10 mils.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 14/092,231 filed Nov. 27, 2013, entitled APRINTABLE MAGNETIC RECEPTIVE COMPOSITE SHEET AND METHOD OF MAKING.

FIELD OF THE INVENTION

Printable magnetic receptive composite sheets are disclosed. Thesecomposite sheets are made by calendering thin layers of magneticcompositions and bonding to a top printable layer wherein the calenderedlayer has a thickness up to 10 mils.

BACKGROUND OF THE INVENTION

Magnetic printable assemblies that will self-adhere to a magneticallyattractable surface are well known. Flexible materials in the form ofsheets or rolls have been commercially available and are typicallyprepared by mixing a powdered ferrite material with a suitable polymericor plastic binder into a uniform mixture and then extruding orcalendering them into sheets or films. The magnetic material may then bepermanently magnetized and the resulting pieces may then be placed on amagnetically attracted surface where they are often used in conveyinginformation. Examples of prior art patents in this field include U.S.Pat. Nos. 7,128,798; 7,338,573; 5,843,329; 5,609,788 and the patentscited in these patents as representative of the prior art. Efforts havebeen made to produce relatively thin printable magnetic receptive filmsor sheets. However, no known methods are believed to allow foracceptable products having relatively thin layers of the binder/magneticmaterial mixture less than 10 mils.

SUMMARY OF THE INVENTION

This invention is directed to a printable magnetic receptive compositesheet having multiple layers. The sheet or film comprises a calenderedmagnetic layer of a thermoplastic binder and a magnetic material and atop printable layer bonded to the calendered layer, wherein thecalendered magnetic layer has a thickness up to 10 mils. Anotherembodiment of the printable magnetic receptive composite of thisinvention has both a top printable layer and a bottom printable layer,or in other words, the composite has the additional feature of beingprintable on both sides. Printable magnetic receptive sheets areprovided that are flexible, readily printable and employed forsecurement to a magnetically attracted surface. The thin printablemagnetic sheets or films have outer surfaces that may be printed with adecorative pattern and/or promotional information. Therefore, they servea very useful function in easily conveying information and/orpromotional material on a variety of surfaces.

The printable magnetic receptive composites of this invention areseveral times more effective in magnetic capacity than presentlyavailable magnetic assemblies. This property is attributable to themethod of making and assembly of the components in the printablemagnetic receptive composite.

The amount of magnetic material in the composite magnetic layer is onthe order of about 50% by wt. with the balance being about 50% by wt. ofthermoplastic binder. More generally, a range of about 50% to 60% by wt.of magnetic material and 60% to 40% by wt. of thermoplastic binder issuitable.

The printable composite is of indefinite length and widths of up toabout 60 inches are obtainable with the relatively thin flexibleconstruction of magnetic composite total layers up to 20 mils.

An additional unique feature of the inventive printable magneticreceptive composite is the inclusion of a prodegradant additive in themagnetic thermoplastic binder and magnetic material layer composition toenhance the compatibility of the components, and yet facilitate thebiodegradability of the composite. Thus, the magnetic receptivecomposite of the invention is especially adapted to be compostable inmunicipal solid waste composting facilities such that it may be degradedby physical, chemical, thermal and/or biological degradation. Therefore,after its usage as a composite to convey decorative patterns and/orother information by attachment of the magnets to a variety of surfaces,the composite may be disposed of by degradation in a municipal solidwaste composting facility.

The printable magnetic receptive composite of this invention, its methodof manufacture and compostability would be further understood withreference to the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

The printable magnetic receptive composite comprises a calenderedmagnetic layer of a thermoplastic binder and a magnetic material,typically a ferrous alloy powder. A printable top layer is bonded to thecalendered layer, wherein the calendered magnetic layer has a thicknessup to 10 mils. In an alternative embodiment, a printable layer is bondedto the calendered layer on both sides of the calendered layer. In thisembodiment, therefore printable surfaces are available on both sides ofthe magnetic receptive composite. In either embodiment, the thickness ofthe calendered magnetic layer is relatively thin and is on the order ofabout 6 to 10 mils. Thin, flexible composites are provided withoutpinholes or voids. A printable layer usually has a thickness of up toabout 6 mils, resulting in an overall dimensional thickness of about 10to 20 mils for the composite. Other features of this invention would bebetter understood with reference to the following drawings anddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an in-line calendering and lamination apparatusfor making a printable magnetic receptive composite of this inventionhaving a printable substrate on one side of the composite.

FIG. 2 is a magnified diagramatic sketch and cross section of theprintable magnetic receptive composite after lamination.

FIG. 3 is a schematic of an alternative laminating section for thecalendering and lamination apparatus of FIG. 1 for making a printablemagnetic receptive composite of this invention having a printablesubstrate on both sides of the composite.

FIG. 4 is a magnified diagramatic sketch and cross section of theprintable magnetic receptive composite after lamination with thealternative laminating section of FIG. 3.

Thermoplastic Binder

The thermoplastic binder for the magnetic material employed in making aprintable magnetic receptive composite may be selected from the classesof olefin polymer, vinyl halide polymer and vinyl acetate polymer asdefined as follows.

A. Olefin Polymer

The olefin polymer employed is most commonly a homopolymer, copolymer,or terpolymer of monomers such as ethylene, propylene or a diene. Theprinciples of this invention are applicable to polymers of unsaturatedhydrocarbons containing one or more pairs of carbon atoms linked by adouble bond. While this invention has been illustrated with specificolefin polymers in the operating examples which follow, it is to beunderstood that this invention is not limited to the specific examples.The olefin monomers that may be polymerized alone or in admixture withother ethylenically unsaturated monomers include, e.g., ethylene;propylene; 1-butene; isobutene; 1-pentene; vinyl benzenes andnaphthalenes such as styrene or vinyl naphthalene; and dienes such asbutadiene, isoprene, cyclopentadiene, and ethylidene norbornene (ENB).Copolymers of such monomers include acrylonitrile-butadiene-styrene(ABS) and styrene-acrylonitrile (SAN). Suitable elastomeric polymers mayalso be biodegradable. Suitable elastomeric polymers include terpolymersof ethylene, propylene, and a diene, such as ENB (EPDM). Otherelastomers include poly(ethylene-butene), poly(ethylene-hexene),poly(ethylene-octene), poly(ethylene-propylene),poly(styrene-butadiene-styrene), poly(styrene-isoprene-styrene),poly(styrene-ethylene-butylene-styrene), poly(ethylene-propylene-diene),and ethylene-propylene. A new class of rubber-like polymers may also beemployed and they are generally referred to as polyolefins produced fromsingle-site or metallocene catalysts whereby ethylene, propylene,styrene and other olefins may be polymerized with butene, hexene,octene, etc., to provide elastomers suitable for use in accordance withthe principles of this invention, such as poly(ethylene-butene),poly(ethylene-hexene), poly(ethylene-octene), poly(ethylene-propylene)and/or polyolefin terpolymers thereof.

B. Vinyl Halide Polymer

The vinyl halide resin employed is most commonly a homopolymer of vinylchloride, i.e., polyvinyl chloride. It is to be understood, however,that this invention is not limited to a particular vinyl halide resinsuch as polyvinyl chloride (PVC) or its copolymers. Otherhalogen-containing polymers or resins which are employed and whichillustrate the principles of this invention include chlorinatedpolyethylene, chlorosulfonated polyethylene, chlorinated polyvinylchloride, and other vinyl halide polymer or resin types. Vinyl halidepolymer or resin, as understood herein, and as appreciated in the art,is a common term and is adopted to define those resins or polymersusually derived by polymerization or copolymerization of vinyl monomersincluding vinyl chloride with or without other comonomers such asethylene, propylene, vinyl acetate, vinyl ethers, vinylidene chloride,methacrylate, acrylates, styrene, etc. A simple case is the conversionof vinyl chloride H₂C═CHCl to polyvinyl chloride (CH₂CHCl—)n wherein thehalogen is bonded to the carbon atoms of the carbon chain of thepolymer. Other examples of such vinyl halide resins would includevinylidene chloride polymers, vinyl chloride-vinyl ester copolymers,vinyl chloride-vinyl ether copolymers, vinyl chloride-vinylidenecopolymers, vinyl chloride-propylene copolymers, chlorinatepolyethylene, and the like. Of course, the vinyl halide commonly used inthe industry is the chloride, although others such as bromide andfluoride may be used. Examples of the latter polymers include polyvinylbromide, polyvinyl fluoride, and copolymers thereof.

C. Vinyl Acetate Polymer

The vinyl acetate polymer employed is most commonly a homopolymer ofvinyl acetate, i.e., polyvinyl acetate. Copolymers of vinyl acetate arealso suitably employed. It is to be understood, however, that thisinvention is not limited to polyvinyl acetate or its copolymers. Othervinyl acetate based polymers which are employed and which illustrate theprinciples of this invention include partially hydrolyzed polyvinylacetate, e.g. polyvinyl alcohol, ethylene-vinyl acetate, vinylchloride-vinyl acetate copolymer or other copolymer types. Vinyl acetatebased polymer, as understood herein, and as appreciated in the art, is acommon term and is adopted to define those polymers usually derived bypolymerization or copolymerization of vinyl acetate monomer with orwithout other comonomers such as ethylene, propylene, vinyl chloride,vinyl ethers, vinylidene chloride, methacrylate, acrylates, styrene,etc. A simple case is the conversion of vinyl acetate to polyvinylacetate wherein the ether oxygen of the ester group is bonded to thecarbon atoms of the carbon chain of the polymer.

Magnetic Material

The term “magnetic material” refers to any material which exhibitspermanent magnetic behavior or is readily permanently magnetized.Typically, a magnetic powder is particularly suitable for use includingthe ferrites and other examples that are well known in the art.Specifically, the following Table describes a suitable ferrous alloypowder that is employed.

TABLE Compound Conc Conc Compound Name (wt %) Element (wt %) Fe2O3Iron(III) oxide 82 Fe 57 MnO Manganese(II) 13 Mn 10 Oxide ZnO Zinc Oxide4.2 Zn 3.3 SiO2 Silicon dioxide 0.34 Si 0.16 Na2O Sodium Oxide 0.32 Na0.24 SrO Strontium 0.13 Sr 0.11 oxide Al2O3 Aluminum 0.11 Al 0.057 oxideZrO2 Zirconium 0.1 Zr 0.078 dioxide CaO Calcium Oxide 0.1 Ca 0.072 P2O5Phosphorus 0.06 P 0.026 pentoxide TiO2 Titanium 0.059 Ti 0.035 dioxideMgO Magnesium 0.05 Mg 0.03 Oxide SO3 Sulfur 0.042 S 0.017 TriooxideCr2O3 Chromium(III) 0.032 Cr 0.022 oxide V2O5 Vandium(V) 0.029 V 0.016oxide Cl Chloride 0.019 Cl 0.019 Nb2O5 Niobium 0.015 Nb 0.01 pentoxide100.606

Auxiliary Agent or Compatibilizer

An auxiliary agent or compatibilizer, used to facilitate the blending ofthe magnetic material in the thermoplastic binder, includes, forexample, an ethylene vinyl acetate (EVA) and a polyolefin elastomer ofthe type defined above. A compatibilizing prodegradant additive such asan organotitante or zirconate may be employed as coupling agents inbinder compositions to essentially increase the stability of thepolymeric compositions. These additives may be used to couple thethermoplastic binder with the magnetic powder in the composition. Inaddition, these organotitanates or zirconates have been found, accordingto U.S. Pat. No. 7,956,101 to act as anaerobic prodegradants therebyachieving a further objective of the composite of this invention byrendering the useful printable magnetic receptive compositesanaerobically degradable in landfills. The entire disclosure of U.S.Pat. No. 7,956,101 is incorporated herein by reference to describe theseadditives and polymer binder compositions for use in the magneticreceptive composites of this invention.

EXAMPLE 1

With reference to the drawings FIGS. 1 & 2, a chlorinated polyethylenepolymer is blended with an auxiliary agent such as EVA and polyolefinelastomer along with the ferrous alloy powder as defined above. Theferrous powder is manufactured by BGRIMM Materials & Technology Co.,Ltd. in China. The percentages in the mixture of the composition includeabout 30% polyethylene, about 50% ferrous alloy powder and about 20%auxiliary agents, such as, the combination of EVA and polyolefinelastomer.

With reference to FIG. 1, the composition is calendered by passing thepolymer binder/magnetic material blend as a continuous sheet 10 througha number of pairs of heated rollers 11 shown diagramatically in FIG. 1.Roller temperatures typically range from about 165° C. to 180° C. duringcalendering. The resulting flexible calendered sheet 12 is thenlaminated to a printable substrate 13 in-line as shown in FIG. 1 to formthe magnetic composite sheet 20 of FIG. 2. The lamination can occur indifferent ways. One way is to bond the printable substrate 13 atsuitable temperature and then cooling the substrate. Another method isto use an adhesive such as a water-based polyurethane adhesive or EVAadhesive to bond the printable substrate 13 to the cooled sheet 12.Either of these methods is acceptable and, in this example, thecomposite 20 of FIG. 1 is a polyethylene terepthalate (PET) film 22having a universal coating 21 for solvent, eco-solvent, latex, UV orepoxy ink printing with magnetic receptive layer 23. The printablecoating contains either a silicone dioxide or a titanium oxide pigment,dispersed in a polymeric binder of water-based polyurethane, water-basedEVA, or polyacrylic emulsion, thereby rendering the printable surface ofthe PET film 22 white. The thickness of the universal coating 21 mayvary, but is on the order of 1 mil. The thickness of the printable layeris on the order of 1 to 6 mil(s), but may vary. The thickness of thecalendered magnetic layer is up to 10 mils, normally 6 to 10 mils.Accordingly, a flexible printable magnetic receptive film 20 with themultiple layers having an overall or total thickness up to about 20mils, preferably 12 mils, is obtained.

EXAMPLE 2

With reference to the drawings FIGS. 3 & 4, an alternative laminatingsection is illustrated for producing the printable magnetic receptivecomposite 30 having printable surfaces 31, 31 on both sides of thecomposite. The composition of Example 1 of polymer binder/magneticmaterial blend is passed as a continuous sheet 10 through a number ofpairs of rollers 11 shown diagramatically in FIG. 1. Suitable rollertemperatures typically range from 165° C. to 180° C. during calendering.The resulting flexible calendered sheet 12 is then laminated on bothsides to a printable substrate 33 as shown in the alternative laminatingsection of FIG. 3 to form a magnetic composite sheet 30 of FIG. 4.Lamination can occur in different ways as described above in Example 1with references to FIGS. 1 & 2, however in this example, the magneticcomposite sheet 30 of FIG. 4 has a printable surface layer on the top 31and bottom 31, or both sides, of the composite 30.

One specific example of a dual printable magnetic composite 30 has a PETfilm 32 with a printable white surface 31, that contains either asilicon dioxide or titanium oxide pigment on both sides of the magneticlayer 12. The thickness of the PET film 32 is about 0.06 mm (about 2.36mils). The top printable layer 31 is about 0.08 mm (about 3.15 mils) inthickness. The bottom printable layer 31 including the magnetic layer 12is about 0.27 mm (about 10.6 mils) in thickness. The film 32 of thebottom layer can be PVC instead of PET. Thus, a specific composite ofthis invention has an overall thickness of about 0.41 mm (about 16 mils)and an overall weight of about 740 gsm.

For comparison with this Example 2, a one-sided printable magneticcomposite of this invention made in accordance with Example 1 has anoverall thickness of 0.34 mm (about 13.4 mils) and a weight of about 610gsm, where the total thickness of a composite is about 0.34 mm (about13.4 mils) with a PET film thickness of about 0.06 mm (2.36 mils) a topprintable film thickness of about 0.07 mm (about 2.76 mils) with amagnetic layer and bottom film having a thickness of about 0.21 mm(about 8.27 mils). This product of Example 1 has a white printable filmsurface with a gray film on the opposite surface attributable to themagnetic layer of the composite, whereas the two-sided printable film ofthis Example 2 has a white printable surface on both sides.

While the printable layer substrate is a polyethylene terepthalate orPVC film in the above examples, it is understood that the substrate forthe printable layer is variable to include any polymeric material,cotton, textile, or paper products, and the like, that may suitablycarry a universal coating for solvent, eco-solvent, latex, UV or epoxytype printing. In view of this description, other embodiments of thisinvention will become apparent to those skilled in the art.

What is claimed is:
 1. A printable magnetic receptive composite sheetcomprising: a calendered magnetic layer containing a thermoplasticbinder and a magnetic material having a front side and a back side, anda printable top layer bonded to at least one of said sides, wherein saidcalendered magnetic layer has a thickness up to 10 mils.
 2. The sheet ofclaim 1 wherein said calendered magnetic layer has a thickness fromabout 6 to 10 mils.
 3. The sheet of claim 1 wherein said printable toplayer is a substrate selected from the group of a polymeric material,cotton, textile or a paper product.
 4. The sheet of claim 3 having anindefinite length and a width of up to about 60 inches with a totalthickness of up to about 20 mils.
 5. The sheet of claim 3 wherein thepolymeric material is a thermoplastic polymer.
 6. The sheet of claim 5wherein said polymer is a polyester or PVC.
 7. The sheet of claim 6wherein the polyester is polyethylene terephthalate.
 8. The sheet ofclaim 3 wherein said printable top layer has a surface with printablecoating deposited thereon.
 9. The sheet of claim 8 wherein saidprintable coating has a silicon dioxide or a titanium oxide pigmentdispersed in a polymeric binder selected from the group of a water-basedpolyurethane, water-based ethylene vinyl acetate polymer and polyacrylicemulsion.
 10. The sheet of claim 1 wherein the said thermoplastic binderis a polymer with a monomeric group of an olefin, vinyl halide and vinylacetate, and copolymers thereof.
 11. The sheet of claim 1 wherein thethermoplastic binder is a chlorinated polyethylene, ethylene vinylacetate, or polyolefin elastomer, and mixtures thereof.
 12. The sheet ofclaim 1 wherein the calendered magnetic layer is bonded to the printabletop layer with the aid of an adhesive.
 13. The sheet of claim 1 whereinsaid calendered magnetic sheet contains an anaerobic prodegradant. 14.The sheet of claim 13 wherein said anaerobic prodegradant is a monomericadduct of an organotitanate or organozirconate.
 15. A method of making aprintable magnetic receptive composite sheet having multiple layers witha front and a back side comprising: calendering a thermoplasticcomposition containing a thermoplastic binder and a magnetic materialinto a continuous magnetic layer having a thickness up to 10 mils and;laminating a printable top layer onto at least one of said magneticlayer sides.
 16. The method of claim 15 conducted at an elevatedtemperature for laminating the magnetic layer to said printable toplayer.
 17. The method of claim 15 wherein the lamination is conductedwith the aid of an adhesive selected from the group of water-basedpolyurethane and water-based EVA.
 18. The method of claim 15 wherein thesaid thermoplastic binder is a polymer having the monomeric group of anolefin, vinyl halide and vinyl acetate, and copolymers thereof.
 19. Themethod of claim 15 wherein said printable top layer is a substrateselected from the group of a polymeric material, cotton, textile or apaper product.
 20. The method of claim 15 wherein said printable toplayer has a surface with a printable coating deposited thereon.
 21. Themethod of claim 15 said printable coating has a silicon dioxide or atitanium oxide pigment dispersed in a polymeric binder selected from thegroup of a water-based polyurethane, water-based ethylene vinyl acetatepolymer and polyacrylic emulsion.